This invention relates to a method and apparatus for joining metallic tubular members by soldering to form a secure leakproof joint. Specifically, this application relates to a method and apparatus for repairing a refrigeration sealed system without the use of a conventional open flame oxygen acetylene torch for making a secure leakproof solder joint between two metallic tubes.
Home appliances which include sealed refrigeration systems, such as refrigerators, freezers, room air conditioners, and the like, occasionally experience failed components, which must then be replaced. To repair such refrigeration systems, the failed component must be removed by cutting or otherwise disconnecting the refrigerant tubes leading to the failed component, removing the failed component, and installing a new component including connecting the new component to the system refrigerant tubes. A conventional method for connecting refrigerant tubes in sealed refrigeration systems has been to align the tubes and manually hold them in position, to heat the tubes to the melting point of solder with an open-flame torch such as an oxygen-acetylene torch, and then to hand feed solder to the joint area. Conventionally, the solder used to make such joints has been a high silver content silver solder which melts at temperatures in the range of 1150.degree. F.-1375.degree. F. Considerable skill is required to make a secure joint in this prior art manner which will not leak so that refrigerant will not escape from the sealed system. Also, since most home appliances are generally quite compact, very little space is available for a service person to make such soldered joints. For instance, in window air conditioners, the tube to tube spacing may be on the order of 5/16 of an inch. Furthermore, by hand feeding solder to a joint area, it is quite possible that the solder will be deposited unevenly so that an excess of solder and flux may enter the sealed system, whereby the compressor may be damaged. Lastly, the uneven deposition of solder may result in microscopic leaks in the joint through which refrigerant may escape from the sealed refrigeration system.
An additional disadvantage of the conventional open-flame method for repairing sealed refrigeration systems is that open-flame repair is not permitted in certain locations, such as high rise apartments. Thus, to repair an appliance, it would have to be removed from the apartment so that it may be repaired in a service shop. This process is not only time consuming and costly and deprives the customer of the appliance for an undesired period of time but may also result in damage to the appliance during its transfer.
A still further disadvantage of the prior art open-flame method for making solder joints is that a low silver content solder cannot be used effectively as the high temperature of the open flame tends to cause evaporation of the tin or lead or both from the soft solder, thereby reducing the effectiveness of the solder material and thus resulting in an unacceptable joint. Conventionally, therefore, high silver content silver solder has been used for making solder joints in sealed refrigeration systems, thus adding further cost to the repair process because of the relatively high price of high silver content solder. In addition, the high temperature of the torch flame tends to soften the refrigerant tubes and causes a relatively high degree of oxidation and scaling, thus potentially resulting in a poor solder joint.
Another prior art method for making solder joints in sealed refrigeration systems has been by the use of an electrically operated apparatus. The structure of one such apparatus is disclosed in U.S. Pat. No. 4,367,397. The apparatus consists of a pair of hinged jaws which are biased in the open position by means of a spring. The jaws of the apparatus must, therefore, be manually held closed by the operator in order to clamp a pair of refrigerant tubes therebetween for soldering. The jaws are secured to a pair of handles so that the operator may grip the handles and squeeze them together to clamp the refrigerant tubes between the jaws. The jaws are also provided with a pair of electrodes which contact the refrigerant tubes. Electric current is then passed through the electrodes whereby the joint area of the refrigerant tubes will be heated. Solder is then fed by hand to the joint area and is melted so that it flows into the tube interface area between the refrigerant tubes to form a joint.
Since soldering of refrigerant tubes requires a relatively large amount of thermal energy, the heat conducted from the joint area through the jaws to the handles will tend to substantially heat up the handles so that they will become too hot to be touched with bare hands. Since the handles must be firmly held by the operator during the soldering process to firmly clamp and position the refrigerant tubes and to ensure good electrical contact, it is desired to dissipate the thermal energy which is conducted through the jaws so that the handles may be kept cool to protect the operator. The prior art tool disclosed in the aforementioned patent is, therefore, provided with large cooling fins which are located between the jaws and the handles to dissipate thermal energy and to prevent the handles from becoming too hot. Such fins add extra cost to the tool and, more importantly, cause the tool to be relatively bulky so that it does not fit in the confined spaces which are encountered in the sealed refrigeration systems of many home appliances. However, even with the provision of such fins, it is often necessary for the operator to wear gloves to operate the prior art soldering apparatus. Furthermore, since the solder is hand fed to the joint area, the above-mentioned disadvantages of hand feeding solder are not solved by the prior art electric soldering apparatus.
It is, therefore, desired to provide a flameless method and apparatus for forming solder joints between two tubes in a refrigeration sealed system which ensures a leakproof, secure solder joint.